Hot gas refrigeration defrosting system with purge means



L. K. QUICK Feb. 15, 1966 HOT GAS REFRIGERATION DEFROSTING SYSTEM WITH PURGE MEANS Filed Jan. 18, 1963 Jnum/m LESTER K. QUICK United States Patent Ofifice 3,234,748 Patented Feb. 15, M966 3,234,748 HGT GAS REFRKGERATION DEFRUSTIN G YSTEM WITH PURSE MEANS Lester K. Quick, 600 Howard St, Eugene, Greg. Filed Jan. 18, 1963, Ser. No. 252,436 14 Claims. (Cl. 62---126) This invention relates to a system for defrosting the evaporator coil of a refrigeration system and, in particular, is directed to a defrosting system which employs the hot compressed gaseous refrigerant from the refrigeration system compressor for the source of heat used in defrosting evaporator coils of the refrigeration system and wherein the refrigerant so used is condensed for subsequent normal use in the refrigeration system. In a normal refrigeration cycle which is employed in this invention, a refrigerant gas such as ammonia, refrigerant 12 or 22 or the like, is compressed in a compressor, passes through a condenser where it gives off heat and changes to a liquid and then passes through an expansion valve to an evaporator coil to absorb heat and change the refrigerant back to a gaseous state for recompressing to complete the refrigeration cycle. The evaporator coil is positioned within a refrigerated fixture, box, display case or cabinet and the heat absorbed by the refrigerant passing through the coil serves to extract heat from the refrigerated fixture and its contents to maintain the fixture at the desired temperature. As is well known, this extracting of heat from the refrigerated fixture and its contents causes frost to form on the evaporator coil which periodically must be removed to maintain proper functioning of the evaporator coil and avoid undesirable build-up of frost on the coil or other parts of the refrigerated fixture.

In modern stores, warehouses and supermarkets, it is common to have numerous refrigerated fixtures, boxes, display cases or cabinets which are refrigerated either by separate, individual refrigeration systems, or by a central refrigeration system supplying compressed-condensed refrigerant to the separate evaporator coils po sitioned in each refrigerated fixture, box, display case or cabinet. It is conventional to provide some type of heater such as an electric heating element in each refrigerated fixture which, when activated, serves to defrost the fixture and evaporator coil relatively automatically and Without manual attenuation to the defrosting phase.

Although this periodic defrosting is essential to the proper operation and maintenance of the refrigerated fixture, it also relatively expensive both in the initial cost of the heaters and in operation due to the amount of power consumed in accomplishing the defrosting by these individual heaters. Generally, the defrosting must be relatively rapid in order to avoid raising the temperature of the refrigerated box an objectionable amount for any substantial length of time. This need for rapid defrosting results in the need for heaters of a relatively high capacity which therefore form a substantial portion of the total cost of the refrigerated fixture, box, display case or cabinet.

As has been well known in the art, hot compressed gaseous refrigerant discharged from the compressor has a heat load capable of defrosting the evaporating coils in refrigerated fixtures. However, in the past a total hot gas defrost was not satisfactory, inasmuch as compressor overloading frequently occurred and the heat load was generally insufficient to effectively defrost both the evaporators and other fixture parts. Furthermore, the change of refrigerant to liquid phase during defrosting is not always complete, consistent or predictable and problems are created in the re-introductionof the refrigerant into the normal refrigeration cycle. For example, if the refrigerant so used for defrosting was completely gaseous, then it could obviously be drawn into the intake of the compressor and recompressed for reuse in the cycle, but if suchrefrigerant were partially condensed its introduction into the intake of the compressor could be extremely harmful to the compressor.

Accordingly, it is a principal object of this invention to provide a novel form of defrosting system for a refrigeration system wherein the hot, compressed gas of the refrigeration system is passed through the evaporator coil to accomplish the defrosting thereof and the refrigerant so used is condensed before re-int-roduction into the normal refrigeration cycle.

Another object of this invention is to provide a defrosting system wherein any gaseous refrigerant remaining in the hot, compressed gaseous refrigerant being passed through the evaporator coils for accomplishing the defrosting will be condensed in a novel form of condensate receiver before the refrigerant is re-introduced into the refrigeration system at that portion of the systern containing compressed-condensed refrigerant.

Another and more detailed object of this invention is to provide a defrosting system for a multiple evaporator refrigeration system wherein the total output of hot, compressed gaseous refrigerant from the compressor or compressors is available for passing through one or more of the evaporator coils at one time for defrosting such coils and the refrigerant used in defrosting is completely condensed in a novel form of condensate receiver, which is cooled by an evaporator coil consuming compressed-condensed refrigerant from the refrigeration system, before the refrigerant used in defrosting is reintroduced into the refrigeration system in a condensed state.

A further and specific object of this invention is to provide a novel form of condensate receiver adapted to receive refrigerant used in defrosting the evaporator coils of a refrigeration system and having an evaporator coil adapted to consume compressed-condensed refrigerant from the refrigeration system for condensing the refrigerant used in defrosting, and wherein apparatus is provided for equalizing the internal pressure of the novel condensate receiver with the refrigeration system receiver and training only condensed refrigerant to the refrigeration system receiver for further use in the refrigeration cycle.

A still further object is to provide such a condensate receiver which is adapted to accumulate non-condensables from the refrigeration system and is provided with means for purging the non-condensables from the receiver and the refrigeration system.

Other and more detailed objects and advantages of this invention will appear from the following description and the accompanying drawings.

The drawing is a diagrammatic illustration showing the preferred form of my invention as incorporated with a plurality of refrigerated fixtures and two compounded compressors.

As found in a normal refrigeration system, means are provided for compressing the refrigerant gas and as shown in the drawings these means may include a standard temperature compressor 10 and a low temperature compressor 11 for supplying hot, compressed gaseous refrigerant through conduit 12 to oil separator 13 and thence through conduit 14 to condenser 15 where the refrigerant is cooled and condensed to a liquid. Although it is not essential to this invention, for increasing the efiiciency I prefer to use the two compressors 10 and 11 rather than only one compressor. With this arrangement compressor 11 takes low pressure gaseous refrigerant from conduit 16 and compresses the same to an intermediate pressure and temperature, the refrigerant then passing through conduit 17 to the hot gas de'superheater 13 and thence through conduit 19 to the intake 211 of the commercial temperature compressor where it is compressed to the proper temperature and pressure for condensing.

The oil separator 13 serves to remove some of the oil present within the gaseous compressed refrigerant which was absorbed from the oil within the compressors. The oil thus separated drains to the reservoir 21 where it is retained for r-e-distribution to the compressors as needed. A de-gassing line 22 connects the upper portion of the oil reservoir 21 to conduit 19 for reducing the pressure within the reservoir 21 to a pressure equal to the intake pressure of compressor 10. This reduction in pressure in reservoir 21 serves to evaporate most of the refrigerant entrapped within the oil separated in the separator 13 and which was drained to the reservoir 21. This evaporated refrigerant is drawn into the intake 20 of the compressor 11) through the degassing line 22 thereby minimizing the amount of refrigerant which will be present within the oil returned to the compressors for re-use. A float valve (not shown) in positioned between the oil separator 13 and the oil reservoir 21 to permit only liquid to pass from the separator to the reservoir, thus preventing the degassing line 22 from drawing hot, compressed refrigerant gas directly from the separator 13. Oil return lines 23 and 24 serve to return the oil from reservoir 21 to the compressors 10 and 11, respectively.

Float valve assemblies 25 and 26 are provided and associated with compressors 1t and 11, respectively, for controlling the oil level in the compressors by controlling the flow of oil through lines 23 and 24 to those compressors. Although this oil separating and returning system is not essential to my invention, I prefer to incorporate the same for the over-all efficiency in automation of the refrigeration, air-conditioning and defrosting systems.

The condensed refrigerant from condenser 15 passes through conduit 27 to an auxiliary standby condenser 28 where any uncondensed gaseous refrigerant is condensed before passing through conduit 29 to the refrigerant receiver 30 of the refrigeration system. While condenser 15 may be of an air-cooled type for use with the air-conditioning system, as described in my co-pending application entitled, Heat Reclaiming System, Serial No. 142,315, filed October 2, 1961, condenser 28 is preferably of a water-cooled type where the flow of water through the condenser 28 from the water source conduit 31 is controlled by a water valve 32 which is responsive in a convential manner through a capillary tube 33 to the inlet pressure of the auxiliary condenser 28. The water used in condenser 28 flows out through line 34 to drain 35. I

The compressed-condensed liquid refrigerant passes from receiver 34 through header 36 to individual branch conduits 37 leading to individual evaporator coils 38, 39, 4t 41, 42 and 43. An expansion valve 44 is provided in each branch conduit 37 for metering the refrigerant to the associated evaporator coil in a conventional manner. The expanded refrigerant is evaporated as it passes through the evaporator coils and there by absorbs heat from each of the refrigerated fixtures, boxes, display cases or cabinets (not shown) within which those evaporator coils are positioned. A separate outlet conduit 45 is connected to each evaporator coil 38, 39, 41B, 41, 42 and 4-3 for passing the expanded-evaporated refrigerant from evaporator coils 38, 3d and 4-0 to a suction header 46 which communicates with suction conduit 47 for returning the gaseous refrigerant to the intake 21} of compressor 10, and for passing the expandedevaporated refrigerant from evaporator coils 41, ".2 and 43 to a suction header 4% which communicates with suction conduit 16 for returning the gaseous refrigerant to the intake of compressor 11, thereby completing the refrigeration cycle. Each of the expansion valves 44 are individually responsive to the pressure and temperature in the conduit 45 associated with that same evaporator coil through any convenient means such as capillary tubes 49 which thereby controls the rate of flow of refrigerant through each expansion valve to the associated evaporator coil.

in the above arrangement with two compounded compressors 111 and 11, it is preferred that the evaporator coils 41, 42 and 43 that have their outlets connected to the lower temperature compressor 11 be associated with lower temperature refrigerated fixtures such as freezers while the other evaporator coils 33, 39 and 40 are associated with higher temperature fixtures such as fresh produce cases. Also, for improved operation, header 3 6 between the branch conduits 37 associated with evaporator coils 40 and 41 may be associated with a conventional intercooler (not shown) for lowering the tem perature of the refrigerant supplied to evaporator coils .1, 42 and 43.

Hand valves 50 may be positioned in each of the conduits 37 and 45 for manual operation to isolate any of the evaporators from the rest of the system for maintenance or repair of that evaporator, associated expansion valve or refrigerated box, display case or cabinet. Hand valves 51 are provided in conduit 27 and header 36 for a manual operation to isolate the auxiliary standby condenser 28 and the receiver 30 for maintenance and repair.

A conduit 52 is connected to header 36 for passing liquid refrigerant to the hot gas de-superheater 18. The flow of refrigerant through conduit 52 may be controlled by solenoid valve 53 or manually controlled by hand valve 54. An expansion valve 55 responsive to temperature sensitive means associated with conduit 19 controls the flow and expansion of the liquid refrigerant to the hot gas de-superheater 13. The refrigerant from conduit 52 is expanded, evaporated and added into the flow of hot, compressed refrigerant passing from conduit 17 through the hot gas de-superheater 13 to conduit 19. This addition of expanded-evaporated refrigerant to the hot, compressed gaseous refrigerant serves to cool the refrigerant, thereby lowering its temperature before entering the intake 21 of compressor 10 through the conduit 19.

Means are provided for accomplishing the defrosting of the evaporator coils 40, 42 and 43 and, as shown in the drawings, these means may include a hot gas header 56, a condensate header 57 and a condensate receiver, generally designated at 58. These means may also be used for defrosting the evaporator coils 38, 39 and 41 or any other evaporator coils in the system upon the provision of apparatus (omitted from the drawings for clarity) similar to that hereinafter described. The hot gas header 56 is connected to conduit 14 and conduits 59, 6t and 61 connect the hot gas header 56 to the outlet of evaporators 40,. 42 and 413, respectively, for supplying hot, compressed gaseous refrigerant to those evaporator coils for defrosting. Conduits 62, 63 and 64 connect the inlet conduits 37 associated with evaporators 411, 42 and 43, respectively, to the condensate header 57 for conducting the gaseous and condensed refrigerant used in defrosting those evaporator c-oils from the coils to the condensate header 57. When it is desired to defrost evaporator 40, for example, normally closed solenoid valves 65 and 66 in the conduits 59 and 62 are opened and normally open solenoid valves 67 and 68 in the outlet and inlet conduits to the evaporator 40 are closed, so that the hot gaseous refrigerant passes from header 56 through conduit 59, through evaporator coil 46, through bypass line 69 and thence through conduit 62 to the condensate header 57. The bypass line 69 is provided so that the refrigerant used in defrosting the evaporator coil 41} is not passed through the expansion valve 44 associated with that evaporator coil in a reverse direction during the defrosting cycle. A check valve 70 is provided in bypass line 69 for permitting refrigerant flow through the bypass line during defrosting of the evaporator coil but prohibiting such flow during the normal refrigeration operation which, if permitted, would render the associated expansion valve 44 ineffective for controlling the rate of flow of refrigerant to evaporator coil 40.

Similarly, normally closed solenoid valves 71 and 72 are provided in conduits 68 and 63, respectively, and normally opened solenoid valves 73 and 74 are provided in conduits 45 and 37 respectively, associated with evaporator coil 42 for defrosting that evaporator coil by opening solenoid valves 71 and 72 and closing solenoid valves 73 and 74. Also, a bypass line 75 and check valve 76 are provided and associated with the expansion valve 44 associated with evaporator coil 42 in order to avoid reverse flow of refrigerant through that expansion valve during the defrosting cycle. Likewise, for defrosting evaporator coil 43, normally closed solenoid valves 77 and 78 are provided in conduits 61 and 64 respectively, normally opened solenoid valves 79 and 80 are provided in conduits 45 and 37 respectively, associated with the evaporator coil 43 and a bypass line and check valve (illustrated, but not numbered) are provided and associated with expansion valve 44, all for use in a like manner. Although I have only shown conduits, valves, bypass lines, and check valves adapted to defrost evaporator coils 40, 42 and 43, it is to be understood that similar conduits, valves, bypass lines and check valves are normally provided with evaporator coi-ls 38, 39 and 41 or any other evaporator coils which may be present for similar operation in defrosting the particular evaporator coil through the use of the hot gas from header 56.

A check valve 81 is provided in each of conduits 62, 63 and 64 to prevent refrigerant within condensate header 57 from flowing from condensate header 57 into the evaporator coils which may be undesirable under certain circumstances. For example, certain refrigerated fixtures preferably operate within a predetermined range and the addition of excessive refrigerant, as would occur through conduits 62, 63 and 64 without the check valves 81, may lower the temperature below that range and damage the products contained in the fixture.

When the hot, compressed gaseous refrigerant passes from header 56 through any one of the evaporator coils, heat is extracted from the gaseous refrigerant to accomplish the melting of the frost present on the coils, and this loss of heat from the refrigerant generally results in condensation of some of the gaseous refrigerant to a liquid state. It is highly undesirable to permit any substantial quantity of condensed refrigerant to enter the intake of a compressor. Even a small amount of liquid refrigerant entering the intake of a compressor will cause objectionable hammering of a compressor, and the introduction of a large quantity of liquid refrigerant into the intake of a compressor would be likely to cause appreciable damage due to the incompressibility of the liquid refrigerant. It has therefore been found impractical to permit the refrigerant used in the defrosting of an evaporator coil to be passed directly to the intake of one of the compressors although this would appear to be the likely solution to the problem of re-introducing the refrigerant used in defrosting back into the normal refrigeration cycle. Further, though it would appear to be a ready solution that the refrigerant used in the defrosting of an evaporator coil merely be re-introduced into the refrigeration system at some portion which contains condensed refrigerant, this is not directly possible. As previously indicated, the pressure of the refrigerant used in defrosting an evaporator coil will neither be consistent nor will it usually exceed the pressure of any one point in the refrigeration cycle containing liquid refrigerant. For example, if it were attempted to introduce the refrigerant used in defrosting from condensate header 57 into conduit 27, the pressure within conduit 27 would normally exceed the pressure within header 57, thus causing the compressed-condensed refrigerant coming from condenser 15 to flow in a reverse direction. through condensate header 57, thereby defeating. the defrosting operation.

In order to completely condense the refrigerant used in defrosting the evaporators and to assure that the refrigerant so condensed can always be introduced into some portion of the refrigeration cycle containing condensed refrigerant, the condensate receiver 58 is provided. The condensate header 57 is connected to the bottom of the tank portion 32 of the condensate receiver 58 for introducing all of the refrigerant, whether gaseous or liquid, used during the defrosting into the tank portion 82. In order to condense any gaseous refrigerant present Within the tank portion 82 and to maintain a low pressure therein so that the refrigerant condensate will be induced to freely flow from header 57 to the tank portion 82, an evaporator coil 83 is provided with the condensate receiver 58 and is positioned within the tank portion 82. A conduit 84 connects the evaporator coil 83 to the header 36 for supplying liquid refrigerant to that evaporator coil. An expansion valve 85 responsive through any convenient means such as capillary tube 86 to the outlet temperature of the evaporator coil 83 serves to expand the liquid refrigerant and thereby cool the tank portion 82 in a normal refrigeration system manner. The expanded-evaporated refrigerant used in evaporator coil 83 passes through conduit 87 to suction header 46 and thence through suction conduit 47 to the intake 20 of the compressor 15) for recompressing. The cooling of tank portion 82 by evaporator coil 83 condenses any gaseous refrigerant present in the refrigerant condensate introduced from header 57 and forms a liquid level 88 within the condensate receiver 58.

The condensate receiver 58 is positioned above the refrigeration system receiver 36) and a drain line conduit 89 leads from the bottom of the tank portion 82 to the refrigeration system receiver 30. A gas pressure equalizing line 90 connects the upper portion of the tank portion 82 to the uppermost portion of the auxiliary condenser 28. If an auxiliary condenser similar to 28 is not provided in the refrigeration system due to the specific requirements of that system, the gas equalizing line 9i) may be connected to the upper portion of the refrigeration system receiver 30. Normally open solenoid valves 91 and 92 are provided in header 57 and conduit 87 respectively, and normally closed solenoid valves 93 and 94- are provided in conduits 89 and 90 respectively. A bleed line 95 is connected to the top of tank portion 82 and is provided with a solenoid valve 96 and hand valve 97. A float switch and control means 98 is provided for automatically controlling the solenoid valves 91, 92, 93 and 94 by means of electrical leads (shown, but not numbered) to drain the tank portion of the condensate receiver 58 when such tank portion becomes nearly filled with condensed refrigerant. As defrosting of the various evaporator coils proceeds the refrigerant used will be supplied through header 57 to tank portion 82 and completely condensed by evaporator coil 83, which whereby causes the liquid level 88 to rise within the tank portion. When the float arm 99 of float switch and control means 98 is raised to the position shown in dotted lines due to the rise in liquid level 88, the control means 98 operates to close solenoid valves 91 and 92 and open solenoid valves 93 and 94. The opening of solenoid valve 94 causes the pressure within tank portion 82. to be equalized to the pressure within the auxiliary condenser 28 (or receiver 30 if no auxiliary condenser is provided) thereby permitting the condensed refrigerant within tank portion 82 to drain through conduit 89 to the refrigeration system receiver 30. When the float arm 99 again reaches its lower position as illustrated, control means 98 operates to close valves 93 and 94 and reopens valves 91 and 92 to re-start the cycle of filling the condensate receiver 58 as further evaporator defrosting occurs. The draining of the tank portion 82 through conduit 98 is relatively rapid and therefore the temporary closing of valve 91 does not substantially impair, such as by causing a back pressure, the continuation of the defrosting of any of the evaporator coils 38, 39, 4t), 41, 4-2 and 43.

In any refrigeration system it is common for a certain quantity of non-condensables to be introduced into, or be present within, the refrigeration system. Generally these non-condensables are comprised of air originally present in the system or entering through a leak in the system, or gases created as a result of partial decomposition of the refrigerant itself, or the oil carried with the refrigerant. The presence of non-condensablcs in a refrigeration system is undesirable for numerous reasons such as their insulating effect which when they are present in the condenser causes the condenser to function at an increased temperature. During the operation of the refrigeration system, the non-condensables are generally washed into the refrigeration system receiver or the auxiliary condenser if such is present within the refrigeration system. Since these non-condensables are gaseous and, if present, will accumulate within the upper portion of the auxiliary condenser 28 of my system, they will flow through gas pressure equalizing lines 96 into the tank portion 82 of the condensate receiver 58 when the valve 94 is opened during draining of the condensate receiver. These non-condensables will be accumulated continually within the tank portion 82 since it is never completely drained.

As is well known, for a particular temperature, a refrigerant gas should have a particular pressure, but if an appreciable quantity of non-condensables are present within the tank portion 82 of the condensate receiver 58, the pressure for that particular temperature will be appreciably greater than if no non-condensables were present. A pressure gauge 100 and a temperature gauge 101 are provided and associated with tank portion 82 for permitting observation of the pressure and temperature of the fluid within the condensate receiver and for continually informing the control means 98 of such pressure and temperature by transmitting respectively corresponding and appropriate varying electrical signals through electrical leads (not numbered). Thus, with a knowledge of the pressure-temperature relationship for the particular refrigerant used in the system, the presence of non-condensables may be detected by observing gauges 100 and 101. Further, appropriate conventional electrical signal comparing means such as a Wheatstone bridge or the like together with a responsive electrical relay are provided in control means 98 for detecting this discrepancy between ideal and actual temperature-pressure relationship which, in turn, serves to operate solenoid valve 96 in bleed line 95 to automatically purge the non-condensables from tank portion 82 when such relationship reaches any predetermined variance from the ideal. Control means 98 is also provided with means for only permitting this purging during normal, nondraining operation of the condenser receiver 58 as when solenoid valve 94 is closed because the high pressure present with valve 94 open would result in the probable loss of at least some refrigerant with the non-condensables. A recording type timing device 102 may be provided and associated with valve 96 to record the frequency of automatic purges of non-condensables so that an abnormal increase in the amount of non-condensables may be readily observed.

Thus it may be seen that I have provided a system whereby the hot compressed gaseous refrigerant supplied by the refrigeration system compressor may be used for defrosting evaporator coils and the refrigerant so used, is introduced back into the refrigeration system in a completely condensed state for performing the useful refrigcrating function. Further, by my arrangement, no pumps are needed to reintroduce the refrigerant used in defrosting back into the refrigeration system, and only that amount of liquid refrigerant is used which is needed for condensing any gaseous refrigerant present within the refrigerant used in the defrosting. Moreover, the non-condensables present or created in the refrigeration system are continually and automatically purged from the system, thereby eliminating the inefficiencies and difficulties caused by the presence of non-condensables.

In normal operation I prefer to defrost only one evaporator coil at a time so that all of the hot, compressed gaseous refrigerant in header 56 is available for passing through that evaporator coil to accomplish the defrosting. With this large quantity of available heat, the defrosting can be accomplished rapidly thereby avoiding an objectionable increase in the temperature of the refrigerated box, display case or cabinet. The solenoid valves which are associated with the evaporator coils, with the hot gas header 56 and with the condensate header 57 may all be controlled by an automatic timing device (not shown) which serves to open and close the appropriate solenoid valves for a predetermined period of time to accomplish the sequential defrosting of the various evaporator coils. The period of time would be determined by considering the type of refrigerated box, its contents, its normal ternperature and through defrosting tests. The only electrical heaters which may be needed to accomplish the complete automatic defrosting of the evaporator coils and refrigerated boxes are those associated with the drains for carrying off the water resulting from the defrosting of the evaporator coils. These electrical heaters would obviously be relatively inexpensive when compared to the heaters normally necessary for defrosting the entire evaporator coils and refrigerated box.

Although I have illustrated and described a refrigeration system and a defrosting system which employ two compressors, an air cooled condenser, an auxiliary condenser, and six evaporators, it is readily apparent and is to be understood that more or fewer compressors, condensers, and evaporators may be used without departing from my invention as individual installation requirements dictate. Having fully described my invention it is to be understood that I do not wish to be limited to the details herein set forth or to the details illustrated in the drawing, but my invention is of the full scope of the appended claims.

I claim:

1. In a defrosting system and a refrigeration system employing a compressor, a condenser, a receiver and at least one evaporator coil, the combination of: means operatively connecting the evaporator coil to the compressor output for conducting hot gaseous refrigerant to the evaporator coil, a condensate receiver, means operatively connecting the evaporator coil to said condensate receiver, said condensate receiver normally being connected solely to the latter said means to receive the defrosting refrigerant from said evaporator coil, an evaporator means operatively connected between the receiver and compressor and in heat transfer relation with said condensate receiver for cooling and condensing the refrigerant passing from the compressor output through the refrigeration system evaporator coil into said condensate receiver, and normally inoperative means selectively operable in response to the level of condensed refrigerant in said condensate receiver for equalizing the pressure within said condensate receiver to the pressure within the refrigeration system receiver and for conducting the condensed refrigerant from said condensate receiver to the refrigeration system receiver.

2. In a defrosting system and a refrigeration system employing a compressor, a condenser, a receiver and at least one evaporator coil, the combination of: means operatively connecting the evaporator coil to the ,COlTlpressor output for conducting hot gaseous refrigerant to the evaporator coil for defrosting the evaporator coil, a condensate receiver, means operatively connecting the evaporator coil to said condensate receiver, said condensate receiver normally being connected solely to the latter said means to receive the defrosting refrigerant from said evaporator coil, an evaporator means operatively connected between the receiver and compressor and positioned in said condensate receiver in heat transfer relation therewith for cooling and condensing the refrigerant passing from the compressor output through the refrigeration system evaporator coil into said condensate receiver, a normally inoperative pressure equalizing conduit connecting said condensate receiver to the high pressure side of the refrigeration system for selectively equalizing the pressure between the said condensate receiver and the refrigeration system receiver, and a normally inoperative drain conduit connecting the bottom of said condensate receiver to the refrigeration system receiver for selectively draining the condensed refrigerant from said condensate receiver to the refrigeration system receiver.

3. In a defrosting system and a refrigeration system employing a compressor, a condenser, a receiver and at least one evaporator coil, the combination of: means operatively connecting the evaporator coil to the compressor output for conducting hot gaseous refrigerant to the evaporator coil for defrosting the evaporator coil, a condensate receiver, means operatively connecting the evaporator coil to said condensate receiver, said condensate receiver normally being connected solely to the latter said means to receive the defrosting refrigerant from said evaporator coil, an evaporator means operatively connected between the receiver and compressor and positioned in said condensate receiver in heat transfer relation therewith for cooling and condensing the refrigerant pass ing from the compressor output through the refrigeration system evaporator coil into said condensate receiver, a pressure equalizing conduit connecting said condensate receiver to the high pressure side of the refrigeration systern for equalizing the pressure between the said condensate receiver and the refrigeration system receiver, a drain conduit connecting the bottom of said condensate receiver to the refrigeration system receiver, and valve means positioned in each of said conduits operable to open positions for equalizing the pressures in said condensate receiver and the refrigeration system receiver and draining the condensed refrigerant from said condensate receiver to the refrigeration system receiver.

4. In a defrosting system and a refrigeration system employing a compressor, a condenser, a receiver and at least one evaporator coil, the combination of: means operatively connecting the evaporator coil to the compressor output for conducting hot gaseous refrigerant to the evaporator coil, 21 condensate receiver, means operatively connecting the evaporator coil to said condensate receiver, said condensate receiver normally being connected solely to the latter said means to receive the defrosting refrigerant from said evaporator coil, an evaporator means operatively connected between the receiver and compressor and positioned in said condensate receiver in heat transfer relation therewith for cooling and condensing the refrigerant passing from the compressor output through the refrigeration system evaporator coil into said condensate receiver, a pressure equalizing conduit connecting said condensate receiver to the high pressure side of the refrigeration system for equalizing the pressure between the said condensate receiver and the refrigeration system receiver, a drain conduit connecting the bottom of said condensate receiver to the refrigeration system receiver, valve means positioned in each of said conduits, and means for actuating said valve means to open positions for equalizing the pressures in said condensate receiver and the refrigeration system receiver and draining the condensed refrigerant from said condensate receiver to the refrigeration system receiver.

5. In a defrosting system and a refrigeration system employing a compressor, a condenser, a receiver and at least one evaporator coil, the combination of: a hot gas header connected to the output of the compressor, a conduit operatively connecting the evaporator coil to said header for conducting hot gaseous refrigerant to the evaporator coil, a condensate receiver having a tank portion, means operatively connecting the evaporator coil to said tank portion of said condensate receiver, said condensate receiver normally being connected solely to the latter said means to receive the defrosting refrigerant from said evaporator coil, an evaporator means operatively connected between the receiver and compressor and positioned in said tank portion of said condensate receiver in heat transfer relation therewith for cooling and con densing the refrigerant passing from the compressor output through the refrigeration system evaporator coil into said tank portion of said condensate receiver, a pressure equalizing conduit connecting said condensate receiver to the high pressure side of the refrigeration system for equalizing the pressure between the said condensate receiver and the refrigeration system receiver, a drain conduit connecting the bottom of said tank portion to the efrigeration system receiver, valve means positioned in said pressure equalizing conduit and said drain conduit operable to open positions for equalizing the pressures in said condensate receiver and the refrigeration system receiver and draining the condensed refrigerant from said condensate receiver to the refrigeration system receiver.

6. in a defrosting system and a-refrigeration system employing a compressor, a condenser, a receiver, at least one evaporator coil, and conduits connecting the evaporator coil to the receiver and to the intake of the compressor, the combination of: conduit means operatively connecting the evaporator coil to the compressor output for conducting hot gaseous refrigerant to the evaporator coil, a condensate receiver, conduit means operatively connecting the evaporator coil to said condensate receiver, said condensate receiver normally being connected solely to said conduit means for receiving the defrosting refrigerant, valve means positioned in each of said conduit means and in each of the refrigeration system conduits operable for separately terminating the flow of refrigerator through the refrigeration system conduits to the evaporator coil and for allowing the flow of hot gaseous refrigerant through said conduit means associated with that evaporator, an evaporator means operatively connected between the receiver and compressor and positioned in said condensate receiver in heat transfer relation therewith for cooling and condensing the refrigerant passing from the compressor output through the refrigeration system evaporator coil into said condensate receiver, and means for equalizing the pressure within said condensate receiver to the pressure within the refrigeration system receiver and for conducting the condensed refrigerant rom said condensate receiver to the refrigeration system receiver.

7. In a defrosting system and a refrigeration system employing a compressor, a condenser, an auxiliary condenser, a receiver, at least one evaporator coil and conduits connecting the evaporator coil to the receiver and to the intake of the compressor, the combination of: conduit means operatively connecting the evaporator coil to the compressor output for conducting hot gaseous refrigerant to the evaporator coil, a condensate receiver, conduit means operatively connecting the evaporator coil to said condensate receiver, said condensate receiver normally being connected solely to said conduit means for receiving the defrosting refrigerant, valve means positioned in each of said conduit means and in each of the refrigeration system conduits operable for separately terminating the flow of refrigerant through the refrigeration system conduits to the evaporator coil and for allowing ill the flow of hot gaseous refrigerant through said conduit means associated with that evaporator coil, an evaporator means operatively connected between the receiver and compressor and positioned in said condensate receiver in heat transfer relation therewith for cooling and condensing the refrigerant passing from the compressor output through the refrigeration system evaporator coil into said condensate receiver, a pressure equalizing conduit connecting said condensate receiver to the auxiliary condenser, a drain conduit connecting the bottom of said condensate receiver to the refrigeration system receiver, valve means positioned in said pressure equalizing conduit and said drain conduit, and control means associated with said condensate receiver for actuating the latter mentioned valve means to open positions for equalizing the pressures in said condensate receiver and the refrigeration system receiver and draining the condensed refrigerant from said condensate receiver to the refrigeration system receiver.

8. The combination of claim 7 wherein the said control means include a float switch associated with said condensate receiver for opening the said valve means in said pressure equalizing and drain conduits when the said condensate receiver is nearly filled and closing those valve means when the said condensate receiver is nearly empty.

9. The combination of claim 8 wherein the said control means closes said valve means poistioned. in the said conduit means connecting the refrigeration system evaporator coil to the said condensate receiver when said condensate receiver is nearly filled and opens that valve means when the said condensate receiver is nearly empty.

10. In a defrosting system and a refrigeration system employing a compressor, a condenser, a receiver and at least one evaporator coil, the combination of: means operatively connecting the evaporator coil to the compressor output for conducting hot gaseous refrigerant to the evaporator coil, a condensate receiver, means operatively connecting the evaporator coil to said condensate receiver, said condensate receiver normally being connected solely to the latter said means to receive the defrosting refrigerant from said evaporator coil, an evaporator means operatively connected between the receiver and compressor and in heat transfer relation with said condensate receiver for cooling and condensing the refrigerant passing from the compressor output through the refrigeration system evaporator coil into said condensate receiver, means for equalizing the pressure within said condensate receiver to the pressure within the refrigeration system receiver and for conducting the condensed refrigerant from said condensate receiver to the refrigerator system receiver, said condensate receiver being positioned above said refrigeration system receiver for accumulating any non-condcnsables present in the refrigeration system, and means associated with said condensate receiver and responsive to deviations of a predetermined magnitude in the inherent pressure-tcmperature relationship of refrigerant in said condensate receiver for purging the non-condensables therefrom.

11. In a defrosting system and refrigeration system employing a compressor, a condenser, a receiver and at least one evaporator coil, the combination of: means operatively connecting the evaporator coil to the comprcssor output for conducting hot gaseous refrigerant to the evaporator coil, a condensate receiver, means operatively connecting the evaporator coil to said condensate receiver, said condensate receiver normally being connected solely to the latter said means to receive the defrosting refrigerant from said evaporator coil, an evaporator means operatively connected between the receiver and compressor and positioned in said condensate receiver in heat transfer reiation therewith for cooling and condensing the refrigerant passing from the compressor output through the refrigeration system evaporator coil into said condensate receiver, a pressure equalizing conduit connecting said condensate receiver to the high pressure side of the refrigeration system for equalizing the pressure between the said condensate receiver and the refrigeration system receiver, a drain conduit connecting the bottom of said condensate receiver to the refrigeration system receiver, valve means positioned in each of said conduits operable to open positions for equalizing the pressures in said condensate receiver and the refrigeration system receiver and draining the condensed refrigerant from said condensate receiver to the refrigeration system receiver, said condensate receiver being positioned above said refrigeration system receiver for accumulating any noncondensables present in the refrigeration system, and means associated with said condensate receiver and responsive to deviations of a predetermined magnitude in the inherent pressure-temperature relationship of refrigerant in said condensate receiver for purging the noncondensables therefrom.

12. In a defrosting system and a refrigeration system employing a compressor, a condenser, a receiver and at least one evaporator coil, the combination of: means operatively connecting the evaporator coil to the compressor output for conducting hot gaseous refrigerant to the evaporator coil, 21 condensate receiver, means operatively connecting the evaporator coil to said condensate receiver, said condensate receiver normally being connected solely to the latter said means to receive the defrosting refrigerant from said evaporator coil, an evaporator means operatively connected between the receiver and compressor and positioned in said condensate receiver in heat transfer relation therewith for cooling and condensing the refrigerant passing from the compressor output through the refrigeration system evaporator coil into said condensate receiver, a pressure equalizing conduit connecting said condensate receiver to the high pressure side of the refrigeration system for equalizing the pressure between the said condensate receiver and the refrigeration system receiver, a drain conduit connecting the bottom of said condensate receiver to the refrigeration system receiver for draining the condensed refrigerant from said condensate receiver to the refrigeration system receiver, a pressure indicating means associated with said condensate receiver, a temperature indicating means associatcd with said condensate receiver, said condensate receiver being positioned above said refrigeration system receiver for accumulating any non-condensables present in the refrigeration system, means associated with said condensate receiver for purging the non-condensables therefrom, and control means responsive to said pressure and temperature indicating means for operating said purging means upon predetermined relationships between pressure and temperature with said condensate receiver indicating the presence of non-condensables.

13. The combination of claim 12, wherein separate valve means are provided and positioned in said pressure equalizing conduit and said drain conduit, and said control means when the said condensate receiver is nearly filled and closing those valve means when the said condensate receiver is nearly empty.

14. in a refrigeration system including compressor, condenser, receiver and first evaporator means normally sequentially connected for refrigeration of said evaporator means, the combination of a defrosting system comprising a condensate receiver, means for selectively connecting the first evaporator means between said compressor means and said condensate receiver for conducting hot gaseous refrigerant to defrost said first evaporator means, said condensate receiver normally being connected solely to the latter said connecting means for receiving the defrosting refrigerant from said first evaporator means into said condensate receiver, second evaporator means in heat transfer relation with said condensate receiver and connected between said receiver and compressor means and normally maintaining a low pressure in said condensate receiver for inducing refrigerant to flow to said condensate receiver from said first evaporator means during defrosting and for substantially completely condensing the refrigerant in said condensate receiver, and means responsive to a predetermined liquid refrigerant level in said condensate receiver for equalizing the pressure within said condensate receiver to the pressure within said receiver means and conducting the condensed refrigerant from said condensate receiver to said receiver means.

References Cited by the Examiner UNITED STATES PATENTS 2,321,964 6/1943 Zieber 62195 2,655,008 10/ 1953 Sloan 62174 2,841,962 7/1958 Richards 62-278 2,978,877 4/1961 Long 62-174 MEYER PERLIN, Primary Examiner. 

1. IN A DEFROSTING SYSTEM AND A REFRIGERATION SYSTEM EMPLOYING A COMPRESSOR, A CONDENSER, A RECEIVER AND AT LEAST ONE EVAPORATOR COIL, THE COMBINATION OF: MEANS OPERATIVELY CONNECTING THE EVAPORATOR COIL TO THE COMPRESSOR OUTPUT FOR CONDUCTING HOT GASEOUS REFRIGERANT TO THE EVAPORATOR COIL, A CONDENSATE RECEIVER, MEANS OPERATIVELY CONNECTING THE EVAPORATOR COIL TO SAID CONDENSATE RECEIVER, SAID CONDENSATE RECEIVER NORMALLY BEING CONNECTED SOLELY TO THE LATTER SAID MEANS TO RECEIVE THE DEFROSTING REFRIGERANT FROM SAID EVAPORATOR COIL, AN EVAPORATOR MEANS OPERATIVELY CONNECTED BETWEEN THE RECEIVER AND COMPRESSOR AND IN HEAT TRANSFER RELATION WITH SAID CONDENSATE RECEIVER FOR COOLING AND CONDENSING THE REFRIGERANT PASSING FROM THE COMPRESSOR OUTPUT THROUGH THE 